This invention relates to a combustion heating apparatus of a type which is designed to maximize or improve the efficiency of heat transfer.
In the field of oil processing, many steps require heat to be applied to the liquid materials to reduce viscosity or to enable separation into the various components. In many cases the heat is applied to the liquid materials by using a simple elongate pipe which extends through the materials generally in a horizontal direction either as a single horizontal length of pipe or including a number of turns thus forming parallel lengths of pipe subsequently leading to a flue. Heat is generated by injecting a stream of propane into the pipe together with a quantity of air so that the propane burns in the air and generates heated combustion products. The heated gases thus pass through the pipe to the flue and as they pass through the pipe they transfer heat through the surface of the pipe to the liquid in the container surrounding the pipe.
In many cases the burner is arranged directly at one end of the pipe and injects a stream of gas into the pipe in a horizontal direction so that combustion takes place within the pipe. This has two significant disadvantages. Firstly a portion of the pipe is taken up by an initial combustion stage which generates little heat, and hence is unavailable for heat transfer. Secondly the flame tends to rise in the pipe so that it links along the upper wall of that portion of the pipe. This leads to significant corrosion in the pipe causing early failure. In addition this asymmetry of the flame within the pipe reduces the efficiency of combustion since it limits the access of the combustion air to one side of the flame. It is in most cases necessary therefore to increase the excess combustion air injected to an amount of the order of 75 percent above theoretically perfect combustion. This excess air thus reduces the temperature of combustion and increases heat losses since more of the heat is carried through the flue for escape into the atmosphere.
The above inefficiencies thus significantly increase the amount of fuel consumed in the heating process with the attendant increase in costs.